Cost effectiveness of screening for subclinical hypothyroidism in the elderly. A decision-analytical model

The value of early detection of subclinical hypothyroidism is the object of a long lasting debate. In this study, we assessed the cost effectiveness of a policy based upon screening for this condition through thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) serum level measurements in the elderly.

A Markov model was developed where hypothetical elderly patients (i.e. > or = 60 years of age), who attend general practitioner (GP) clinics for periodic health examinations in a primary-care setting in Italy, made transitions between health states at annual interval for 15 years, thus allowing an estimation of the average cost and of the expected average number of quality-adjusted life-years (QALY). In this model, patients were assumed to be seen at annual intervals by GPs for clinical examination and serum cholesterol level measurement, to which a TSH, T3 and T4 serum measurement was added. In the base-case analysis, TSH was measured every 5 years and, if abnormal, T3 and T4 serum levels were also determined. Costs were analysed from the perspective of the Italian National Health Service (NHS) and reflected 1996 values.

In the base-case analysis, the additional benefit estimated from testing a female population for subclinical hypothyroidism every 5 years was 0.36 QALY, with a cost per QALY gained of 668,298 lire (L). The expected gain in QALY for men was 0.20 and the cost per QALY gained was L270,322. In general, the best cost-effectiveness profile was seen with testing every 3 years. Results were sensitive to variations in the prevalence of disease among the target population, both in men and women.

Our study indicates that a screening policy for subclinical hypothyroidism in the elderly population could be worthwhile. However, as the costs could be significant when applied at the population level, this policy deserves further assessment through well-designed primary research.